Water temperature in Switzerland

How warm Swiss lakes and rivers get

Switzerland swims in its lakes, its rivers and its public lidos, known locally as Badis. Lowland lakes such as Lake Zurich and Lake Constance warm up from June and usually peak in late July or August. Deep lakes at the foot of the Alps, like Lake Lucerne, stay a little fresher, while Lake Lugano in Ticino tends to be milder. The Aare, Rhine, Reuss and Limmat carry cooler Alpine water but become popular for river swimming in high summer. Most Badis open in May and close in September.

The 244 sites draw on several sources. The Federal Office for the Environment, BAFU, measures water temperature continuously at its hydrological stations on rivers and lakes. Many Badis report their own water temperature, and those values flow straight in. Eawag measuring probes add data for some lakes. Large lakes such as Lake Geneva are complemented by Alplakes lake models, whose values are calculated and shown with a model label.

Cantonal laboratories test water quality at official bathing spots throughout the season. For river swimming in the Aare or Rhine, know your entry and exit points in advance, keep well clear of bridge piers and weirs, and look out for boats. On the larger lakes, flashing orange storm warning lights signal rising wind, and the Bise or Föhn can build waves quickly. After thunderstorms, rivers may turn murky and rise fast.